Flexible Non-Enzymatic Glucose Sensors via Electrospray Reduction of Copper Nanoparticles on Laser-Induced Graphene

Non-enzymatic glucose sensors have the advantages of low cost, high sensitivity, stability, and good shelf life. The porous laser-induced graphene (LIG) on flexible substrates obtained by a simple fabrication process shows good conductivity and porous morphology advantageous for sensing. Herein, flexible and non-enzymatic glucose biosensors are fabricated based on a composite of copper nanoparticles (CuNPs) anchored on LIG. The fabrication process involved a non-contact, simple, and cost-effective electrospray reduction (ESR) deposition technology, where an aqueous copper ion solution serves as the ESR precursor. The positively charged micro-scaled droplets generated by electrospray act as micro-reactors, in which the potential difference between the charged droplets and the negatively biased substrate drives the in situ reduction of Cu2+ to CuNPs. This non-contact ESR process enables the conformal deposition of CuNP catalysts on LIG, utilized here for glucose sensing. The size and distributions of the CuNPs can be tuned by the ESR parameters. The optimized sensors demonstrate excellent performance for glucose detection in KOH alkaline electrolyte, exhibiting a sensitivity of 622.9 μA·mM-1·cm-2, a limit of detection of 29.73 μM, and a wide linear range from 0.05 to 10 mM, as well as remarkable repeatability and selectivity for glucose. The ability for detection of glucose in neutral PBS buffer (pH 7.4) was also demonstrated. The ESR process provides a rapid and green fabrication of reliable non-enzymatic glucose sensors and presents a promising processing strategy for wearable and flexible health monitoring devices.